﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Linq.Expressions;
using System.Data.Objects.DataClasses;
using System.Reflection;

namespace BaseLib.Data
{
    public class ParameterRebinder : ExpressionVisitor
    {
        private readonly Dictionary<ParameterExpression, ParameterExpression> map;

        public ParameterRebinder(Dictionary<ParameterExpression, ParameterExpression> map)
        {
            this.map = map ?? new Dictionary<ParameterExpression, ParameterExpression>();
        }

        public static Expression ReplaceParameters(Dictionary<ParameterExpression, ParameterExpression> map, Expression exp)
        {
            return new ParameterRebinder(map).Visit(exp);
        }

        protected override Expression VisitParameter(ParameterExpression p)
        {
            ParameterExpression replacement;
            if (map.TryGetValue(p, out replacement))
            {
                p = replacement;
            }
            return base.VisitParameter(p);
        }
    }

    public static class DataExtensions
    {
        public static Expression<T> Compose<T>(this Expression<T> first, Expression<T> second, Func<Expression, Expression, Expression> merge)
        {
            // build parameter map (from parameters of second to parameters of first)
            var map = first.Parameters.Select((f, i) => new { f, s = second.Parameters[i] }).ToDictionary(p => p.s, p => p.f);

            // replace parameters in the second lambda expression with parameters from the first
            var secondBody = ParameterRebinder.ReplaceParameters(map, second.Body);

            // apply composition of lambda expression bodies to parameters from the first expression 
            return Expression.Lambda<T>(merge(first.Body, secondBody), first.Parameters);
        }

        public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second)
        {
            return first.Compose(second, Expression.AndAlso);
        }

        public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second)
        {
            return first.Compose(second, Expression.Or);
        }

        public static string GetPrimaryKeyName(this EntityObject ent)
        {
            string tempPrimaryKeyName = "";

            PropertyInfo[] props = ent.GetType().GetProperties();
            foreach (PropertyInfo prop in props)
            {
                foreach (var attr in prop.GetCustomAttributes(typeof(EdmScalarPropertyAttribute), false))
                {
                    EdmScalarPropertyAttribute edmProp = (EdmScalarPropertyAttribute)attr;
                    if (edmProp.EntityKeyProperty)
                    {
                        tempPrimaryKeyName = prop.Name;
                        break;
                    }
                    if (!String.IsNullOrEmpty(tempPrimaryKeyName))
                        break;
                }
                if (!String.IsNullOrEmpty(tempPrimaryKeyName))
                    break;
            }
            return tempPrimaryKeyName;
        }

        public static T GetPrimaryKeyValue<T>(this EntityObject ent)
        {
            PropertyInfo pkey = ent.GetType().GetProperty(ent.GetPrimaryKeyName());

            return (T)pkey.GetValue(ent, null);
        }
    }
}
